It is recognized that additional sources of energy are needed for America's sustained industrial growth. There exists an ever present danger in depending too heavily on fossil fuels, particularly those fuels imported from foreign sources. Fossil fuels (hydrocarbons) represent a limited supply of stored energy which may be released only during a combustion process. By burning hydrocarbons mankind has spewed billions of tons of toxic pollutants into the atmosphere. It therefore makes sense from both an environmental and economic standpoint to develop alternative sources of fuel.
Hydrogen is a fuel which does not produce pollutants, water being its only combustion product. Hydrogen has many industrial uses in the production of fertilizers, dyes, drugs, plastics, hydrogenated oils and fats and methanol and is used in many industries. It is also used as a rocket fuel.
1. Field of the Invention
This invention relates to a process for the production of hydrogen from anaerobically decomposed organic materials, including materials such as those found in landfill materials and sewage sludge, by applying an electric potential to and thereby creating a current through the anaerobically decomposed organic material and thereby forming hydrogen.
2. Description of Related Art
The established processes for producing hydrogen are: (1) steam reforming of hydrocarbons, (2) partial oxidation of coal, (3) electrolysis of water, and (4) direct use of solar radiation (photovoltaic method).
Steam-reformation of hydrocarbons and partial oxidation of coal are disadvantageous in that hydrocarbon fuels are consumed. Production of hydrogen by electrolysis of water, a relatively simple and non-polluting process, is costly and therefore economically disadvantageous for most industrial applications because the amount of energy needed for electrolysis of water exceeds the energy obtained from the combustion of the resulting hydrogen. Photovoltaic methods of hydrogen production have inherent inefficiencies related to access to solar radiation.
Unlike the methods for production of hydrogen outlined above, the process of the present invention does not depend on fossil fuels or the somewhat random appearance of sunlight to produce hydrogen. The present process converts what are typically waste materials into hydrogen, while simultaneously reducing the mass of said materials and/or reducing the treatment time of such materials by application of a relatively small electric potential to said materials. The process of this invention uses raw materials typically found in, among other places, municipal waste sites and sewage treatment plants and produces more energy, in the form of the chemically stored potential energy of hydrogen, than is required to produce the hydrogen.
A method of producing hydrogen from sugars is discussed in Energy and the Environment, Proceedings of the 1st World Renewable Energy Congress, Reading, UK, 23-28 September 1990. S. Roychowdhury and D. Cox ("Roychowdhury"). This method involves the production of hydrogen from pure sugars such as glucose or maltose.
Roychowdhury reports the initial production of hydrogen upon inoculation of a sugar solution with so-called "landfill inocula". To obtain landfill inocula, materials were obtained from various depths in a landfill, dried, ground (to obtain "landfill powder") and then incubated in situ. The incubated culture medium was observed to produce carbon dioxide and methane, primarily, and little else, indicating the presence of highly methanogenic flora in the innoculum. The supernatant from this culture medium, or in some cases the landfill powder, were used as inocula.
Roychowdhury discloses that upon inoculation of various sugar solutions with the landfill supernatant or landfill powder, the sugar solution produced hydrogen and carbon dioxide, and no methane or oxygen; indicating the presence of hydrogen-producing bacteria present in the landfill inoculum and/or landfill hydrogen. Hydrogen production decreased with increasing acidity, but could be increased by neutralizing the pH. A low voltage (approximately 3-4.5 V) electric current passed through Roychowdhury's sugar solution resulted in continuous hydrogen production, without neutralization. Variations of this technique were attempted with several combinations of inocula and sugar solutions, each resulting in sustained hydrogen production.